The only thing you can only control is whether or not YOU personally watch someone's Story.

But because Snapchat has an auto-play feature, where Snap Stories play back to back automatically, people accidentally watch each other's Stories all the time.

And when it's your ex's Story (and you totally don't care about him at all and are totally fucking over him, seriously guys, why are you asking?!), this little feature can be annoying, to say the least.